Pump-pressure loaded-with unloading relief valve



Nov. 8, 1949 E. H. SCHANZLIN 2,487,732

PUMP-PRESSURE LQADED--WITH UNLOADING RELIEF VALVE Filed Feb. 19, 1948 ZSheets-Sheet l fnverzlr'x Erna; i ,H c/icz rgl z'n Nov. 8, 1949 fruuenl or Ernes'f hrjc/zanjlin Patented Nov. 8, 1949 PUMP-PRESSURE LOADEDWITH UNLOADING RELIEF VALVE Ernest H. Sehanzlin,

Borg-Warner Corpora poration of Illinois Cleveland, Ohio, assignor to tion, Chicago, 111., a cor- Application February 19, 1948, Serial No. 9,354

3 Claims.

This invention relates to liquid pressure generators or pumps, and particularly to positive fixed displacement intermeshing gear type pumps including axially adjustable end plate or bushing means effective when in engagement with the side faces of the gears to provide a pumping seal therewith and being held in such position by liquid pressure generated by the corresponding gears.

In certain installations it has been found important to provide an arrangement for limiting the top pressure that the gear pump can gen erate irrespective of the speed at which the pump may be driven, an example of such an installation being that for supplying pressure fluid for feathering aircraft propellers. Prior to the present invention it has been the common practice to provide an unloading valve arrangement operable to divert the entire output of pressure liquid delivered by the pump when the pressure rises above a predetermined maximum value. This solution to the problem has necessitated the use of a large unloading valve of sufficient capacity to handle all or a major portion of the pump output volume. The provision of a valve of such large capacity involves excessive manufacturing costs and other disadvantages, which are overcome by the present arrangement.

It is an object of this invention to provide a working pressure liquid generator of the fixed displacement intermeshing gear type having bushing means engaging the gear side faces for providing a pumping seal, this bushing means being held in pumping seal engagement by means of the liquid pressure generated by the gears and being further particularly characterized by the provision of a pilot control valve assembly responsive to the occurrence of a bushing actuating pressure of a predetermined maximum value for preventing the development of any higher bushing actuating pressure while maintaining said maximum value of pump output pressure.

Other and more specific objects and advantages of the present invention will become apparent from a reading of the following specification taken in connection with the appended drawings forming a part thereof and wherein:

Fig. 1 is an axial cross section view of a preferred form of pressuregenerating arrangement, taken substantially on the line l-l of Fig. 3 and bringing out to advantage the structural formation of the bushings that provide the pumping seal with the gear side faces;

Fig. 2 is a broken away sectional view taken 2 substantially along the line 2-4 of Fig. 1 bringing out to advantage the arrangement of the pilot control valve effective to relieve pressures in excess of a predetermined value of pressure from communication with the back side .of the pressure loaded bushings;

Fig. 3 is a cross sectional view taken substantially on the line 3-3 of Fig. l bringing out to advantage the construction of the front or gear engaging faces of the bushings as well as the manner in which the pressure from the output side of the gears is directed to the back faces of the bushings for the purpose of pressure loading the same to provide the pumping seal;

Fig. 4 is a simplified schematic view intended to bring out even more clearly the manner in which the pressure loading of the bushings is effected and particularly the arrangement of the pilot control valve for assuring that the pressures in excess of a predetermined maximum value are relieved from the pressure loaded side of the bushings; and

Fig. 5 presents comparative curves bringing out the relationship of the pressure generated by the gears to the pressure acting on the rear faces of the bushings as the rate of rotation is increased, revealing clearly that these two values of pressure remain the same until the predetermined maximum value of output pressure has been reached whereupon the pilot control valve begins to open and relieve any further development of increased pressure acting on the rear face of the bushings.

Referring in greater detail to the figures of the drawings, a gear pump indicated generally at l0, illustrating a preferred embodiment of the present invention, includes essentially an enclosing housing i'i formed with a pump chamber indicated generally at i2 having an inlet l3, an outlet M and containing a pair of intermeshing gears l5 and I6 effective when driven to continuously move liquid from inlet I3 out of outlet Housing H is preferably made up of two sections, lib and He, held together by suitable fastening means I l f for facilitating assembly and I disassembly. Each of the gears are provided with axially oppositely extending journals l5a, l5b, Isa, iBb, journal l6?) extending outwardly and terminating in a driving coupling connector I60. Stationary bushings indicated generally at i! engage the gear side faces on one side for the purpose of providing a pumping seal and bearing for the journals Mia and Mia, while bushings indicated generally at it engage the opposite gear side faces for the purpose of providing a pumping seal and bearing for journals lb and Ilib, of output pressure has been generated, this point these latter bushings being arranged to be presbeing indicated at Pl. Any tendency for the pressure loaded and controlled in a special manner sure acting on the rear faces ilb of the bushings forming the particular subject matter to which to rise above this value is counteracted by the the present invention is directed. 5 opening of pilot control valve 25 and hence the Referring particularly to Figs. 2, 3 and; lit will output pressure P is correspondingly limited to a be seen that bushing front faces I 8a arefir ormaldefinite maximum value not appreciably above ly held in pumping seal engagement with the adthat value of pressure at which the pilot valve Jacent side faces of the corresponding gears by beings to open. While the upper portion of the means of pressure generated by the gears and 10 curve P is shown slightly above the correspond acting on rear pressure responsive motive suring portion of curve B for purposes of illustratfaces l8b, this pump output pressure being diing the relationship, it will be realized that presgrected to the rear faces lilb through axially exsure P can never have any appreciable value tending passage l9. With reference to Fig. 3 it above that of pressure B. This is necessarily the will be-seen that passage is is defined by the wall 5 case since the generation of pressure P depends "of housing II and the adjacent converging porupon the effectiveness of pressure B in holding tions of the radial flanges of the bushings, on the bushingsinpressure sealing relationship with the outlet side of the gears. The opposite corthe corresponding gear side faces. responding area of convergence between the up- The present invention may be considered a per and lower bushing flanges that would nor- 90 special application or improvement over Lauck mally provide a passage placing the rear faces et al. Patent No. 2,420,622; Lauck Patent No.

of the bushings in communication with the low 2,437,791; and Wichorek pending application pressure side of the gears is closed by a plug 20. 687,379 filed July 31, 1946, now Patent No. 2,472,- Particular attention is directed to the pilot 031 issued May 31, 1949, and reference may be had control valve arrangement indicated generally at thereto for a more detailed understanding of 25 and functioning to maintain pressure on rear the respective features claimed therein pressure responsive surfaces lb of the bushings, being e rib h i detail only t t extent up to a selected predetermined maximum value necessary for an understanding of the present of pressure. Upon the generation of this presinvention. sure value, his pilot con l v lve will begin to Relief valve assembl 30 functions to maintain p n a thereby p v t th uildi up of any a small diflerential of pressure on seal assembly higher pressure acting on rear surfaces lab. The 3|, the occurrence of any pressure above this exact value of pressure above which pilot control value operating to cause ball check valve 30a to valve 25 will begin to open may be readily conopen and relieve any such excess pressure. Coil trolled by the choice f coil compr on pr as compression spring 30b is selected in accordance 25a functioning to urge the ball check valve 25b with the desired pressure to be maintained on into engagement with the valve seat. It will be seal assembly 3! and is received within tubular noted that ball check valve 251) is seated against closure 30c held in position by any suitable means the direction of flow of fluid from passage i id in such as, for example, pin 30d. communication with the rear pressure responsive Seal assembly 3| may be of any suitable form surface Nb of the bushings, the outlet side of ball effective to provide a rotary seal. This assemcheck valve 251) communicating through passage bly i illust at d a bei composed lie with pump inlet l Passage serves t member 3la carried by Journal extension iBb place the bushing outer terminals in communicahaving a radial forward face held in fluid seal tion with the low pressure inlet l3. Pil 0 engagement with a corresponding face on insert trol valve 25 preferably comprises the hollow closshoulder 3 lb mounted in housing 0 ure plug 25c confined within housing bore Hg by means ofacompression spring Me. by a pin 25d. One end of coil compression spring The gear face engaging surfaces [8a are formed 25a is disp s d n p u 2 0 n n a n t r with radially extending depressions lad for prewith, the other end of spring 25a engaging ball 60 venting entrapment of the liquid being pumped. check valve 25b and urging the same into con- Relief recess tact with the valve seat, which comprises the with the low pressure area through axially exlower end of sleeve insert 25e; Sleeve insert 25c tending channels |8f The relative areas of is mounted in a suitably enlarged portion 25f pumping seal providing surfaces I84: and pressure of passage I Id, and the lower end of t Sle ve responsive surface i8b are so arranged that as extends s ight y o the upper Portion Of 110115- long as the pressure generatedby the pump does 8 bore 9. It will be noted, too. that t e uppe not exceed the value of pressure for which pilot portio of c o u p 0 is substantially control valve 25 is set, the bushings l8 will be duced in outer diameter, thereby to deil With held in pumping seal engagement with the gear he uppe portion 0 housing bo a and the eX- side faces, while any tendency to generate a tended portion of sle ve s t 256 a Substantially higher pressure results in faces |8a moving annular valve chamber 259', with which the left axially away from the corresponding gear side end, as viewed in Fig. 2, of passa c faces suiliciently to prevent any such increase cates. It will be understood that closure plug 25c i generated pressure, may be arranged in any other desired manner Whil th present inven such, for example, as in threaded relationship in connection t aspeci with housing bore Hg for the purpose of adjustit is t b u too th ing t compression of spring 25a to vary the top ample rather than by way of limit dischar p e o the p pthe invention is to be defined by the appended Referring to Fig. 5 it will be seen that as the claims which should be given a $0 rate of rotation of the pump is increased and surate with the prior art. the generated outlet pressure rises, the pressure I i curve B ind c ng t pressure acting 011 1. In a pump of the class described, a housing tive surface 18b of the bushings coincides with having an inlet and an outlet aperture formed the output pressure curve P until a selected value 76 therein, a pair of intermeshing ears for pumption has been described fic embodiment thereof pening I la,

ing liquid from said inlet to said outlet apertures, movable bushings associated with said gears, a pressure loading chamber formed in said housing and having one side thereof defined by the outer side surfaces of said movable bushings so that pressure in said chamber is exerted against said bushings, tending to move said bushings into sealing engagement with said gears, a conduit connecting said chamber to the outlet side of said pump to admit liquid under pumping pressure to said chamber, and means for controlling the loading pressure in said chamber comprising means defining a second conduit connecting said chamber to the inlet side of said pump, a ball check valve disposed in said conduit so as to open in response to pressure applied from said chamber, and resilient means for holding said valve in closed position.

2. In a pump of the class described, a housing having an inlet and an outlet aperture formed therein, a pair of intermeshing gears for pumping liquid from said inlet to said outlet apertures, movable bushings associated with said gears, a pressure loading chamber formed in said housing and having one side thereof defined by the outer side surfaces of said movable bushings so that pressure in said chamber is exerted against said bushings, tending to move said bushings into sealing engagement with said gears, a conduit connecting said chamber to the outlet side of said pump to admit liquid under pumping pressure to said chamber, and means for controlling the loading pressure in said chamber comprising means defining a second conduit connecting said chamber to the inlet side of said pump, a ball check valve disposed in said conduit so as to open in response to pressure applied from said chamber, resilient means for holding said valve in closed position, and means for adjusting the pressure exerted by said resilient means on said valve.

3. In a pump of the class described, a housing having an inlet and an outlet aperture formed bushings, tending to move said bushings into sealing engagement with said gears, a conduit connecting said chamber to the outlet side of said pump to admit liquid under pumping pressure to said chamber, and means for controlling the loading pressure in said chamber comprising means defining a passage connecting said chamber to the inlet side of said pump, said passage including a bore formed in said housin a portion of said bore comprising a valve chamher, a first conduit connecting at one end to said loading chamber and at its other end to said valve chamber and a second conduit connecting at one end to said valve chamber and at its other end to the inlet side of said pump, a sleeve insert disposed in said first conduit, a portion of said insert extending into said valve chamber, the extended portion of said insert defining a valve seat, a hollow closure plug mounted in said bore and having one end of reduced outside diameter terminating adjacent but in spaced relation to the extended portion of said insert, a ball check valve carried by said plug, and resilient means in said plug for urging said valve against said valve seat.

ERNEST H. SCI-IANZLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,944,648 Saussard Jan. 23, 1934 2,437,791 Roth et al. Mar. 16, 1948 

